Nowadays, a bright, dazzling smile has become one of the benchmarks of beauty. Dental offices advertise it in and television commercials subtly project it as the formula for physical perfection. In fact, the television is rife with campaigns about toothpaste that can give you a set of pearly, white teeth in a matter of minutes. Which is why it’s no surprise that tooth whitening has now formed part in the skin whitening rage, and thus become part of the beauty regimen. And this has only fueled the people’s obsession to making themselves whiter, be it with their complexion or with their teeth.
But why the perpetual obsession for fairer skin and whiter teeth? Perhaps it has stemmed from the perception that white is synonymous with cleanliness and health. And that a beautiful smile can cure one’s failing self-confidence, attract more people, and increase the chance to be more successful in life. This belief is further reinforced by pictures of models and movie stars flashing their brighter smiles, thereby setting the trend for whiter teeth.
But what is the truth behind this trend? Are teeth really supposed to be white and bright?
What gives the tooth its natural color?
The tooth has two basic anatomic parts, the crown and the root. The crown is that part seen in the oral cavity while the root is the one embedded in the alveolar bone. The crown is covered by enamel, which is the hardest structure in the body, while the main bulk of the tooth from crown to root is made up of another mineralized structure called dentin. Inside the tooth is a space filled with an agglomeration of blood vessels and nerves called the dental pulp.
The dentin, located underneath the tooth’s enamel surface, is opaque and naturally yellowish in color. However, the degree of yellowness differs from person to person. On the other hand, the enamel which is the outer covering is translucent and naturally grayish, though some describe it as bluish-white. Taking all these into account, one can say that the human tooth is not white because its natural shade is off-white and slightly yellowish. Its translucent appearance comes from the underlying dentin and the enamel.
The enamel is somewhat porous and with age, the teeth absorb stains from the foods and beverages we consume. Some foods and beverages contain more chromogenic (staining) agents than others. Examples are red wine, tea, and coffee. Smoking also darkens the teeth because of the cigarette’s nicotine content whose by-products can cause brownish stains on the teeth.
Systemic exposure to certain types of medicines can also cause yellow teeth discoloration. For instance, antibiotic tetracycline is notoriously known to cause discoloration especially when taken at the age when teeth are still developing. This medicine can cause a generalized band-like, yellow-brown to blue-grey staining of the teeth. Thus, tetracycline and its other forms and derivates are seldom prescribed for pregnant women and children who are eight years old and below.
As the person ages, the enamel becomes thinner and the dentin’s yellowish layer tends to become more apparent. One should not also expect the permanent teeth to be as white as primary (temporary/ milk) teeth. Primary teeth are whiter than permanent teeth due to the structural differences of their enamel and dentin.
How to safely make our teeth whiter?
Tooth bleaching can reverse the process of discoloration and even make teeth whiter. The most common chemical agent used for tooth bleaching is hydrogen peroxide. It is applied on the surface of the tooth, although the period of application depends on the method used. The hydrogen peroxide oxidizes the stains on the tooth, leaving a whiter surface.
There are three methods of tooth whitening or bleaching. The first one is in-office bleaching where the procedure is entirely done in a dental office. The concentration of hydrogen peroxide used is high, around 35%. This concentration can be caustic to the tissues, hence, some precautions should be taken like isolating the teeth and covering the gums. Some in-office bleaching use light to hasten the reaction.
The second one is home bleaching in which dentists prescribe a home bleaching kit to the patient, fabricate a custom tray where the patient will place the bleaching agent (also hydrogen peroxide but of lower concentration). The latter should dispense the bleaching on the tray and wear the tray for around 2 hours a night for a week. After one week, the dentist would then check for any whitening effect and advise the patient to continue the procedure if needed. To avoid overzealous bleaching, the dentist would usually prescribe only a week’s worth of bleaching solution.
The third one is over the counter bleaching agents, usually in the form of toothpaste and strips. The patient applies the bleaching solution himself without any professional supervision. Care should be taken when these products are used as their main component is still hydrogen peroxide. Over bleaching is the common adverse effect which results to increase in the translucency of the teeth and paves the way to a grayish appearance.
Patients should be advised that tooth hypersensitivity during and after the bleaching procedure is a common and fleeting side effect. The sensitivity is related to the dehydration that the teeth undergo during the bleaching procedure, causing differences in osmotic pressure and sensitizing the odontoblastic processes (nerves of the teeth). To prevent and manage bleaching-related hypersensitivity, the patient is sometimes advised to brush with a desensitizing toothpaste containing potassium nitrate (e.g. Sensodyne and Crest Sensitive) for two weeks prior to the procedure. Potassium nitrate is used to inactivate the nerves, thereby decreasing pain response. Most bleaching agents contain desensitizers like ACP (amorphous calcium phosphate) and fluoride to prevent or alleviate hypersensitivity.
Patients are also advised not to eat or drink highly pigmented food and beverages such as coffee, tea, and red wine as well as avoid smoking for at least two weeks after the procedure and during the procedure (if home bleaching is used).
Previously, dentists wait for around two to three weeks before placing bonded restorations (tooth-colored fillings) as the hydrogen peroxide can affect the structure of the enamel and prevent good bonding to the tooth. However, newer bleaching agents which also contain hydrogen peroxide have a neutral pH of 7 which prevents alteration of the enamel. This way, tooth colored fillings can be placed immediately after bleaching.
It is important for both the dentist and the patient to know which bleaching product should be used. Dentists should also inform patients that immediately after bleaching, the teeth will appear white due to dehydration but become slightly darker after half an hour or so once the teeth rehydrate. This will be the final color of the bleached teeth. Also, rebound or reversal to a slightly darker color may occur after one to two years and a retouch may be necessary.
In conclusion, tooth bleaching has now become one of the most in-demand esthetic procedures. It is a fast, easy and relatively safe procedure which can have dramatic esthetic results that improve a person’s overall appearance. However, expectations should be set by both the patient and the dentist prior to the procedure. Teeth are by nature off-white, contrary to the so-called standard Hollywood white. Attaining gleaming, white teeth should be approached with caution, and patients should be well-informed about the side-effects that come with bleaching.